This invention relates to catheters that can by steered by external controls. More particularly the invention relates to such catheters that can assume complex three dimensional curves. In addition, the invention relates to the use of such complex curves to ablate arrhythmia substrates in body tissue.
Cardiac mapping is used to locate aberrant electrical pathways and currents emanating within the heart. Such aberrant pathways cause irregular contractions of the heart muscle resulting in life-threatening patterns or disrhythmias.
Ablation of cardiac tissue to create long curvilinear lesions within the heart is also desired for treatment of various disorders such as atrial fibrillation. Various steering mechanisms for catheters carrying such electrodes have heretofore been developed and used.
To access various endocardial sites, physicians have used a number of different catheters and techniques, each of which provides a different characteristic. The use of catheters having limited steering characteristics increases the risk inherent in any catheterization procedure and limits the accessibility of many potential ablation sites.
Site access using standard distal tip steerable catheters is less of a problem because those catheters position a single electrode into contact with the endocardium and a specific electrode orientation is not required. Problems of endocardial site access are accentuated when trying to simultaneously position multiple electrodes into intimate tissue contact. In this scenario, standard steerable catheter configurations orient multiple electrodes in planes emanating about the axis of the introduction vessel.
A need has thus existed for catheters which, in the nonlinear environment found within the heart as well as other body cavities, are capable of being steered to place ablation elements at a number of locations while creating intimate tissue contact throughout the length of all active ablation elements.
Particularly, a need has existed for a catheter which could effectively and accurately form curves in more than one plane for better access or tissue contact. Previous attempts to provide such devices are represented by U.S. Pat. No. 5,383,852 wherein there was suggested the use of steering wire extending from a central lumen of a catheter radially outward to the periphery of a distal end component. Another suggestion in represented by U.S. Pat. No. 5,358,479 wherein a single pull cable is attached to the distal end of a shim which has two flat sections that are twisted relative to each other. This arrangement, however limits the device to bending, first, of the more distal portion of the shim followed by subsequent bending of the more proximal section, thus limiting the procedures using the device.
The present inventions provides a catheter, usable in both diagnostic and therapeutic applications, that enables a physician to swiftly and accurately steer the distal section of the catheter containing the ablation and/or mapping element(s) in multiple planes or complex curves within the body of a patient. The catheters that embody the invention allows physicians to better steer a catheter to access various endocardial sites. In its broadest aspect, the invention provides catheters which enable a physician to position ablation and/or mapping electrodes inserted within a living body by manipulation of external controls into intimate contact with an interior body surface that curves in more than one plane.
One aspect of the invention provides a catheter having more than one steering mechanism for bending the distal section by external manipulation into more than one curvilinear direction. Movement of the individual controls results in bending of the distal section at more than one location and in more than one direction. Thus the ease of accessing and measuring electrical activity in all portions of the heart is increased.
In accordance with another embodiment, the catheter steering assembly may include a proximal section containing a preformed portion in conjunction with a distal steering mechanism which enables steering in a different plane that is non-parallel to the bending plane of the preformed proximal section, and/or improving tissue contact by moving the focal point of the steering mechanism to increase the angle of steering capable of applying force against the endocardial surface. This configuration may be accomplished by preforming the proximal section of the catheter into the desired curve or manipulating a preformed wire or other support structure which, when freed from the constraints of a sheath such as the catheter main body, causes the proximal section to assume the preformed shape.
In accordance with a further embodiment of the invention, a loop catheter has a preformed proximal end and a moveable wire attached to the distal end of the spline housing the ablation element(s). The preformed proximal end enables the loop to access varying planes relative to the catheter axis.
Further, objects and advantages of the invention will become apparent from the following detailed description and accompanying drawings.